1. Field of the Invention
The present invention relates to a semiconductor device, and particularly to a thin-film semiconductor chip.
2. Related Background Art
Currently, as the functions provided for cellular phones, digital AV apparatuses and IC cards continue to be improved, there is a corresponding increase in the need for highly integrated, thin and compact chips that can be mounted in these devices. Thin chips are also used in the fabrication of an SiP (System in Package) or an MCP (Multi Chip Package), for which a plurality of semiconductor chips are mounted, at high density and in multiple layers, in a single package. Hence, to satisfy the demand for thin film semiconductors, the manufacture of thin chips is required.
An example technique whereby the bottom surface of a silicon substrate is ground to obtain a thin semiconductor chip is disclosed in Japanese Patent Laid-Open Publication No. Hei 7-302769.
The following manufacturing method is disclosed in this publication.
A diffusion layer and an electrode are formed on the top surface of a silicon substrate, and while the bottom surface is ground using a grindstone, a crystal defect layer is introduced. Titanium, Monel and silver are deposited, in the named order, on the bottom surface, to form the crystal defect layer and obtain an ohmic electrode. As the objective of this publication, an ohmic electrode is obtained by using a grindstone having a large grain size to intentionally introduce a crystal defect.
Generally, a semiconductor chip is sealed using a resin, and is attached, at its bottom surface, to an assembly board. According to the above described manufacturing method, since a crystal defect layer is deposited on the bottom surface of the semiconductor chip, an ionized contaminant from the assembly board can be prevented from entering the semiconductor chip through its bottom surface. However, a contaminant that has passed through the resin, can not be prevented from entering the semiconductor chip at a side surface.